#include "TLV.h"

static const uint16_t crc16_table[256] = 
{
    0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
    0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
    0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
    0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
    0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
    0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
    0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
    0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
    0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
    0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
    0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
    0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
    0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
    0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
    0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
    0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
    0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
    0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
    0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
    0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
    0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
    0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
    0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
    0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
    0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
    0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
    0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
    0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
    0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
    0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
    0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
    0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
};

/**  
 * @brief CRC16校验  
 *  
 * 根据X25协议进行CRC16校验，计算给定数据的CRC16校验码。  
 *  
 * @param data 数据指针  
 * @param length 数据长度  
 *  
 * @return 计算得到的CRC16校验码  
 */
uint16_t crc16_x25_check(uint8_t* data, uint8_t length)
{
	unsigned short crc_reg = 0xFFFF;

	while (length--)
		crc_reg = (crc_reg >> 8) ^ crc16_table[(crc_reg ^ *data++) & 0xff];
	
	crc_reg = (uint16_t)(~crc_reg) & 0xFFFF;

	return crc_reg;
}

/**  
 * @brief 封装TLV包
 *  
 * 将value_len个字节大小的value封装成TLV的格式压入给定的缓冲区  
 *  
 * @param buffer 缓存区指针
 * @param buf_len 缓冲区长度
 * @param value 要发送的TLV数据
 * @param value_len 数据所占的字节数
 * @param tag 标签，可用来标识这是一个什么类型的数据或者什么类型的报文
 *  
 * @return 返回值为协议报文大小，如果出错则返回 0  
 */
uint16_t tlv_packet(uint8_t *buffer, uint8_t buf_len, void *value, uint8_t value_len, uint8_t tag)
{
	uint16_t crc16 = 0, protocol_len = sizeof(tlv_head_t) + value_len;
	tlv_t *p_protocol_format = NULL;

	// buffer空间不够
	if(buf_len < protocol_len + 2) return 0;

	// 为协议格式数据申请内存
	p_protocol_format = (tlv_t *)malloc(protocol_len);
	if(p_protocol_format == NULL)	return 0;

	p_protocol_format->head.Delimiter = TLV_Delimiter;
	p_protocol_format->head.Length = value_len;
	p_protocol_format->head.Tag = tag;
	memcpy(p_protocol_format->value, value, value_len);

	// 计算head和value的crc16校验码
	// crc16 = crc16_x25_check((uint8_t*)p_protocol_format, protocol_len);
	// 计算value的crc16校验码
	crc16 = crc16_x25_check((uint8_t*)value, value_len);

	// 拷贝到buffer
	memcpy(buffer, p_protocol_format, protocol_len);
	// 注意 CRC16 是小端存储还是大端存储
	*(buffer + protocol_len) = (crc16 & 0xFF00) >> 8;
	*(buffer + protocol_len + 1) = crc16 & 0x00FF;

	// 释放内存
	free(p_protocol_format);
	p_protocol_format = NULL;

	return protocol_len + 2;  // 加上两个字节的crc16校验码
}

/**  
 * @brief 解析TLV包  
 *  
 * 从给定的缓冲区中解析TLV包，并获取标签和值的长度。  
 *  
 * @param buffer 缓冲区指针  
 * @param buf_len 缓冲区长度  
 * @param value_len 数据的长度指针  
 * @param tag 标签指针  
 *  
 * @return 返回值为解析出的TLV包中value的位置  
 * @return 返回0表示解析失败  
 */
uint16_t tlv_parse(uint8_t *buffer, uint8_t buf_len, uint8_t *value_len, uint8_t *tag)
{
	tlv_t *p;
	uint8_t i;
	uint16_t crc16 = 0, protocol_len = 0;

	// 找到帧头的位置
	for(i = 0; i < buf_len && (uint8_t)buffer[i] != TLV_Delimiter; i++) ;
	if(i >= buf_len)	return 0;                       // 找不到帧头
	if(buf_len - i <= sizeof(tlv_head_t)) return 0;   // buffer中的数据不完整

	p = (tlv_t *)(buffer + i);
	protocol_len = p->head.Length + sizeof(tlv_head_t);
	if(buf_len < i + protocol_len + 2)	return 0;     // buffer中的数据不完整

	// crc16验证
	// crc16 = crc16_x25_check(buffer + i, protocol_len);
	crc16 = crc16_x25_check(buffer + i + sizeof(tlv_head_t), p->head.Length);
	// 注意 CRC16 是小端存储还是大端存储
	// if( (crc16 & 0x00FF) !=  *(buffer + i + protocol_len) && ((crc16 & 0xFF00) >> 8) !=  *(buffer + i + protocol_len + 1) )
	if( (crc16 & 0x00FF) !=  *(buffer + i + protocol_len + 1) && ((crc16 & 0xFF00) >> 8) !=  *(buffer + i + protocol_len) )
		return 0;

	*tag = p->head.Tag;
	*value_len = p->head.Length;
	return i + sizeof(tlv_head_t);  // value的位置
}
